On the formation and crystal structure of the Pd<sub>6</sub>B phase

Berger, Tilmann Georg; Leineweber, Andreas; Mittemeijer, E. J.; Sârbu, C.; Düppel, Viola; Fischer, Peter

doi:10.1524/zkri.2006.221.5-7.450

Cited by 11 publications

(3 citation statements)

References 37 publications

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“…Indeed, the lattice parameters observable by diffraction methods are sometimes determined by the microstructure, e.g., in Pd 6 B. 48 However, it is impossible to clearly distinguish a long-range ordered phase with a certain amount of disorder from a GeTe-type phase with defect layers that does not exhibit long-range periodicity.…”

Section: E Influence Of the Powder-particle Size On The Establishmenmentioning

confidence: 99%

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

et al. 2010

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Rewritable data-storage media and promising nonvolatile random-access memory are mainly based on phase-change materials ͑PCMs͒ which allow reversible switching between two metastable ͑amorphous and crystalline͒ modifications accompanied by a change in physical properties. Although the phase-change process has been extensively studied, it has not been elucidated how and why the metastable crystalline state is kinetically stabilized against the formation of thermodynamically stable phases. In contrast to thin-film investigations, the present study on bulk material allows to demonstrate how the cubic high-temperature phase of GeTe-rich germanium antimony tellurides ͑GST materials͒ is partially retained in metastable states obtained by quenching of bulk samples. We focus on compositions such as Ge 0.7 Sb 0.2 Te and Ge 0.8 Sb 0.13 Te, which are important materials for Blu-ray disks. Bulk samples allow a detailed structural characterization. The structure of a multiply twinned crystal isolated from such material has been determined from x-ray diffraction data ͑Ge 0.7 Sb 0.2 Te, R3m, a = 4.237 Å, c = 10.29 Å͒. Although the metrics is close to cubic, the crystal structure is rhombohedral and approximates a layered GeTe-type atom arrangement. High-resolution transmission electron microscopy ͑HRTEM͒ on quenched samples of Ge 0.8 Sb 0.13 Te reveal nanoscale twin domains. Cation defects form planar domain boundaries. The metastability of the samples was proved by in situ temperature-dependent powder diffraction experiments, which upon heating show a slow phase transition to a trigonal layered structure at ca. 325°C. HRTEM of samples annealed at 400°C shows extended defect layers that lead to larger domains of one orientation which can be described as a one-dimensionally disordered long-periodical-layered structure. The stable cubic high-temperature modification is formed at about 475°C. Powder diffraction on samples of Ge 0.8 Sb 0.13 Te with defined particle sizes reveal that the formation of the stable superstructure phase is influenced by stress and strain induced by the twinning and volume change due to the cubic → rhombohedral phase transition upon quenching. The associated peak broadening is larger for small crystallites that allow relaxation more readily. Consequently, the degree of rhombohedral distortion as well as the appearance of superstructure reflections upon annealing is more pronounced for small crystallites. The same is true for samples which were slowly cooled from 500°C. Hence, the lattice distortion accompanying the phase transition toward a stable trigonal superstructure is, to a certain degree, inhibited in larger crystallites. This kinetic stabilization of metastable states by stress effects is probably relevant for GST phase-change materials.

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Section: E Influence Of the Powder-particle Size On The Establishmenmentioning

confidence: 99%

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

et al. 2010

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“…Direct measurement of the boron content in the MZ region was not possible due to the limitations of the SEM/FESEM-EDX method, despite the optimization of the accelerating voltage to 5 keV, as is suggested in [ 50 ]. However, the identification of the Ni-B and Cr-B phases (respectively, the dark gray phase and the fine black phase in Figure 7 ) was possible on the basis of detecting the presence of this element in the appropriate areas of MZ ( Table 2 ), analysis of the relevant equilibrium phase systems [ 33 , 34 , 35 , 36 , 37 , 38 ] and macroscopic XRD analysis of this zone ( Figure 8 ). In addition, this is also indicated by the results of the hardness measurements ( Figure 12 ).…”

Section: Discussionmentioning

confidence: 99%

“…Analysis of the relevant binary and ternary phase equilibrium systems indicates that, despite of the creation of Ni-Pd solid solution in an unlimited range of concentrations [ 32 ], Pd supplement in Ni-Cr-B-Si BFMs does not protect against the formation of brittle phases. Moreover, besides typical borides/silicides, a number of binary Pd-Si, Pd-B and ternary Ni-Pd-Si intermediate phases have been reported [ 33 , 34 , 35 , 36 , 37 , 38 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Structural Components in Hastelloy X Joints Brazed with Ni-Pd-Cr-B-Si Alloy

Baranowski

Senkara

2023

Materials

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The brazing of structural high-temperature-resistant nickel alloys is a predominant method in manufacturing jet engines in the aircraft industry. Ni-Cr-base brazing filler metals (BFMs) containing B and Si as the melting point depressants are used for this purpose. The presence of the latter can lead to the formation of brittle constituents in the joints, decreasing their strength, toughness and creep resistance. The structures of Hastelloy X nickel superalloy joints brazed with Palnicro 36M BFM are presented in this paper along with the mechanical properties of their particular phases as a function of brazing time. Indentation hardness, Martens hardness, reduced modulus and creep coefficient were measured using the instrumented indentation method. The elastic part of the indentation work was also calculated. Pd forms an unlimited solution with Ni, but its high content in BFM does not fundamentally change the general joint structure known from other Ni-superalloy–Ni-BFM systems. However, new Pd-containing phases are emerging. The hardest components were Ni-B and Cr-B boride phases and Pd-Ni-Si phase in MZ and the boundary of DAZ and BM. MZ reduces the plasticity of a joint to the highest extent. The hardness of particular parts in the joints and the elastic portion of the indentation work decreased with the increase in brazing time, while the reduced modulus of the indentation contact and indentation creep increased. The results of indentation creep measurements indicate that all structural components of the joints were less susceptible to creep than the parent material at room temperature.

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Rediscovering the Crystal Chemistry of Borides

2017

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For decades, borides have been primarily studied as crystallographic oddities. With such a wide variety of structures (a quick survey of the Inorganic Crystal Structure Database counts 1253 entries for binary boron compounds!), it is surprising that the applications of borides have been quite limited despite a great deal of fundamental research. If anything, the rich crystal chemistry found in borides could well provide the right tool for almost any application. The interplay between metals and the boron results in even more varied material's properties, many of which can be tuned via chemistry. Thus, the aim of this review is to reintroduce to the scientific community the developments in boride crystal chemistry over the past 60 years. We tie structures to material properties, and furthermore, elaborate on convenient synthetic routes toward preparing borides.

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On the formation and crystal structure of the Pd₆B phase

Abstract: The crystal structure of the Pd

Cited by 11 publications

References 37 publications

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

Mechanical Properties of Structural Components in Hastelloy X Joints Brazed with Ni-Pd-Cr-B-Si Alloy

Rediscovering the Crystal Chemistry of Borides

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On the formation and crystal structure of the Pd6B phase

Abstract: The crystal structure of the Pd

Cited by 11 publications

References 37 publications

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

Influence of stress and strain on the kinetic stability and phase transitions of cubic and pseudocubic Ge-Sb-Te materials

Mechanical Properties of Structural Components in Hastelloy X Joints Brazed with Ni-Pd-Cr-B-Si Alloy

Rediscovering the Crystal Chemistry of Borides

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On the formation and crystal structure of the Pd₆B phase